The Great Western Railway 2900 Class or Saint Class, which was built by the Great Western Railway's Swindon Works, incorporated several series of 2-cylinder passenger steam locomotives designed by George Jackson Churchward and built between 1902 and 1913 with differences in the dimensions.

During the first decade of the twentieth century the Chief Mechanical Engineer, George Jackson Churchward, designed or acquired a number of experimental locomotives with different wheel arrangements and boiler designs to help him plan for the future motive power needs of the railway.

[1] The first of these was a two-cylinder 4-6-0 locomotive, designed in 1901 whilst Churchward was still the Chief Assistant of his predecessor William Dean.

Between 1902 and 1905 Churchward built and tested three prototype locomotives with detail differences, before using the third as the basis for the production series.

98, was built at Swindon Works in March 1903 (Lot 138) to a similar design but with a taper boiler, re-designed valve gear layout and cylinders and a shorter wheelbase.

171 formed the basis of the main production series, introduced in 1905, although at this time Churchward was still unsure of the relative merits of the 4-4-2 and 4-6-0 wheel arrangements.

A second series of ten similar locomotives appeared in May 1906 (Swindon Lot 164), numbered 2901–10 and named after historical, mythological or poetical 'Ladies'.

In May 1906 Charles Collett, then assistant manager of Swindon Works, supervised a demonstration run of number 2903 Lady of Lyons, newly released from the erecting shop.

[10][11][12] A third series of twenty further locomotives appeared during August and September 1907 (Swindon Lot 170), numbered 2911–30 and named after Saints.

The framing for these had long curved ends under the cab and over the cylinders, which greatly improved the rather angular appearance of the earlier locomotives.

2925 Saint Martin was rebuilt with smaller wheels in December 1924 to become the prototype Collett 4900 and renumbered 4900 but still carrying the same name.

Churchward had recognized this limitation by the introduction of his GWR 4700 Class 2-8-0 design with 5 ft 8 in (1.727 m) driving wheels in 1919, intended for express goods trains.

2925 Saint Martin with 6 ft (1.829 m) driving wheels to become the prototype of his successful Hall Class locomotives.

[17] Moreover they also influenced similar engines on other railways such as the LMS "Black Fives", the LNER B1s and the BR Standard Class 5s.

2935 was rebuilt with Lentz-style rotary cam poppet valve gear,[19] which remained in use until the engine was scrapped in 1948.

[20] The class incorporated many revolutionary advances which were influential in British locomotive design for the next fifty years.

Tuplin commented; "No other locomotive design, except perhaps Stephenson's 'Rocket', has represented such a long leap in the right direction as GWR No.

None of the original Saints survived into preservation, so the Great Western Society purchased GWR 4900 Hall Class 4-6-0 No.

The project finally began in earnest in 1995, by which time engineering capability in the preservation movement had greatly increased.